Ab initio modeling of oxygen-vacancy formation in doped-HfOx RRAM: Effects of oxide phases, stoichiometry, and dopant concentrations

Doping techniques have been widely investigated to improve the performance and reliability of resistive random-access memory. In this paper, oxide phases, non-stoichiometry, and dopant concentrations are identified as three critical factors that affect the characteristics of doped HfOx. Using ab initio calculations, their effects on Al, Ti, and Si dopants are thoroughly investigated and compared with experimental studies. In particular, the inconsistent observations regarding the effects of Al dopants on forming voltages are explained by the variation of oxygen stoichiometry. Only non-stoichiometric oxide will activate the dopant effects to significantly reduce the forming voltages.